Friday, 21 May 2010

Volcanic Ash Cloud Disruption

As everybody is probably already well aware the Icelandic volcano Eyjafjallajökull began erupting on 20th March this year. Since then the resultant ash cloud has been intermittently interrupting flights across Europe. The last time this volcano erupted in 1821 it continued to do so for over a year fuelling speculations that the chaos will continue throughout the summer holiday season. UK research aircraft have been involved in a number of flights in an attempt to gain as much information as possible about this phenomenon. Initial flights were carried out by the NERC Dornier 228 Airborne Research and Survey Facility (ARSF) aircraft on the 15th and 16th April when layers of ash and sulphorous material were identified. Since then both the Dornier and the FAAM BAe-146 aircraft have been involved in further scientific flying to characterise the ash plume.

 Image from NASA's Terra satellite on May 11 at 12:15 UTC.The volcano is represented by a red rectangle. Credit: NASA Goddard / MODIS Rapid Response Team

Due to the importance of this activity and the potential duration of the eruptions the BORTAS campaign has been postponed until a similar period next year. But don't worry, that doesn’t mean that we have nothing to do for the next 12 months. Despite the absence of the aircraft the satellite data will be available and the ground-based measurements will still be going ahead. This means that we can still carry out the forecasts that will tell us where biomass burning plumes are likely to go, and see how well these predictions compare with what the instruments see. Modelling activities will also continue and so we will have plenty to report, and hopefully activities this summer will ensure that we are well prepared when the campaign comes around and allow any potential difficulties to be identified.

Tuesday, 4 May 2010

The Dalhousie LIDAR

On the 14th and 15th April the first full science team meeting was held in Edinburgh. The two days consisted of discussions of logistics and presentations from participants, but also provided a brilliant opportunity to meet some of the people we will be spending a month with in the summer. Having been on a few research campaigns before I thought I knew quite a lot of people from the UK atmospheric science community, but on receiving the list of attendees I realised that there were rather a lot of unfamiliar names. You might think this would make the meeting less fun, but it turned out that I knew very little about the science that most of these guys did and so I found myself really interested in the presentations being given.

An example of one of these interesting presenters is Tom Duck from Dalhousie University in Canada. Tom operates an instrument called a Raman Lidar. Lidar is actually another acronym standing for Light Detection And Ranging. It is similar to Radar (Radio Detection And Ranging) which is often used to track aircraft or ships. In this case laser light is used to detect particles in the atmosphere, also known as aerosols, by measuring the laser radiation scattered by these particles. Above is a picture (taken from Tom’s presentation) of the laser beam from the lidar coming from what Tom calls his ‘penthouse laboratory’. It is apparently a popular site around Halifax and I’m not surprised, it looks like something from a comic book or sci-fi movie.
And the plots of data from this instrument are just as cool; above is an example of a plot from Tom’s lidar data when biomass burning plumes were overhead. The warm colours indicate the greatest backscatter showing the presence of a thick layer of aerosol at a height of between 3.5 and 5.5 km. It will be interesting to see what the data shows during our campaign in July, hopefully some similar events will be observed! More details about Tom's work can be found on the Dalhousie University Atmospheric-Optics Laboratory webpages.